Re: [Xen-devel] [PATCH v2 1/2] xen: x86: copy back tsc info, not pointer to tsc info in domctl

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2015-05-26 at 13:25 +0100, Jan Beulich wrote:
> >>> On 26.05.15 at 13:14, <ian.campbell@xxxxxxxxxx> wrote:
> > --- a/xen/arch/x86/domctl.c
> > +++ b/xen/arch/x86/domctl.c
> > @@ -856,13 +856,16 @@ long arch_do_domctl(
> >              ret = -EINVAL;
> >          else
> >          {
> > +            xen_guest_tsc_info_t info = { 0 };
> > +
> >              domain_pause(d);
> > -            tsc_get_info(d, &domctl->u.tsc_info.info.tsc_mode,
> > -                         &domctl->u.tsc_info.info.elapsed_nsec,
> > -                         &domctl->u.tsc_info.info.gtsc_khz,
> > -                         &domctl->u.tsc_info.info.incarnation);
> > +            tsc_get_info(d, &info.tsc_mode,
> > +                            &info.elapsed_nsec,
> > +                            &info.gtsc_khz,
> > +                            &info.incarnation);
> >              domain_unpause(d);
> > -            copyback = 1;
> > +            if ( copy_to_guest(domctl->u.tsc_info.out_info, &info, 1) )
> > +                ret = -EFAULT;
> >          }
> >          break;
> >  
> 
> I have to admit that I don't see the point of this change when patch
> 2 basically undoes it all.

I thought so at first but the restructuring in the second patch was
large enough that I didn't want to mix it in with an actual functional
change. Plus the second patch does more than undo it, it removes "info."
from the domctl access.

Ian.



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